The present invention relates to torsion damping assemblies in general, and more particularly to improvements in assemblies which can be utilized in motor vehicles to compensate for fluctuations of torque which is transmitted between the crankshaft of the internal combustion engine and the input shaft of the change-speed transmission. Still more particularly, the invention relates to improvements in torsion damping assemblies of the type wherein several coaxial flywheels can rotate relative to each other within predetermined limits and against the opposition of one or more yieldable dampers. One of the flywheels can receive torque directly from the crankshaft of the engine and another flywheel can transmit torque to the input shaft of the transmission, preferably through the medium of a friction clutch.
It is already known to install between the aforementioned flywheels an antifraction bearing which centers of the flywheels and ensures that they rotate about a common axis, and to non-rotatably secure one race of the antifriction bearing to the other flywheel. In spite of their highly satisfactory damping characteristics, such assemblies failed to gain acceptance in the automotive and other industries even though they are (in many respects) ideally suited for the transmission of torque between the crankshaft of an internal combustion engine and the power train which transmits torque to the wheels of a motor vehicle. The primary reason for such lack of acceptance is that the useful life of the antifriction bearing between the flywheels is very short, i.e., the antifriction bearings constitute the critical elements of such damping assemblies because their useful life is much shorter than that of other component parts. The reasons for the short useful life of the antifriction bearings are numerous and they are attributable in part to pronounced fluctuations of the magnitude and/or direction of transmitted torque. Moreover, the races of the antifriction bearing between the flywheels can only perform rather limited angular movements relative to each other, i.e., the extent of such angular movement does not exceed the extent of maximum permissible angular movement of the flywheels relative to each other. This is particularly undesirable when a vehicle which embodies the torsion damping assembly is under load and causes the races of the antifriction bearing to perform low-amplitude but high-frequency angular movements relative to one another. The rolling elements (e.g., balls) between the races of the antifriction bearing then perform recurring and relatively short back-and-forth rolling movements with attendant pronounced wear upon the adjacent portions of the races. In other words, the wear is limited to relatively small portions of the races so that such portions of the races develop recesses for the adjacent portions of the rolling elements. The formation of such recesses is the first stage of rapid deterioration and ultimate destruction of the races. Furthermore, the rolling elements can cause flaking or chipping of the adjacent portions of the races, and the thus segregated fragments promote rapid destruction of the antifriction bearing. Still further, limited back-and-fourth movements of the rolling elements do not suffice to ensure adequate lubrication of the races and/or rolling elements.